Researchers in Germany have raised the alarm after discovering bacteria immune to antibiotics in several streams, rivers and lakes. Thousands of people in Germany die each year from diseases caused by these pathogens.

Dangerous pathogens resistant to multiple types of antibiotics were found at 12 locations in the northern German state of Lower Saxony, according to a report by broadcaster NDR on Tuesday.

Researchers took sediment and water samples from the different sites and sent them to the Dresden University of Technology and the German Center for Infection Research in Giessen for testing.

The NDR-commissioned study detected so-called multidrug-resistant gram-negative bacteria (MDRGN bacteria) at all the locations, as well as strains resistant to crucial reserve antibiotics known as drugs of “last resort.”

“This is really alarming,” Tim Eckmanns from the Robert Koch Institute said in an interview with NDR. “These pathogens have apparently arrived in the environment, and on such a scale that surprises me.”

“The danger is that they’ll spread and then strike back against humans,” he added.

While resistant pathogens are known to live and even thrive in the environment, NDR said they are not systematically monitored as part of water pollution tests.